Re-evaluation and modification of dehydrogenase activity tests in assessing microbial activity for wastewater treatment plant operation.

Reliable and cost-effective methods for monitoring microbial activity are critical for process control in wastewater treatment plants. The dehydrogenase activity (DHA) test has been recognized as an efficient measure of biological activity due to its simplicity and broad applicability. Nevertheless, the existing DHA test methods suffer from imperfections and are difficult to implement as routine monitoring techniques.

Electron Transfer Mechanism at the Interface of Multi-Heme Cytochromes and Metal Oxide.

Electroactive microbial cells have evolved unique extracellular electron transfer to conduct the reactions via redox outer-membrane (OM) proteins. However, the electron transfer mechanism at the interface of OM proteins and nanomaterial remains unclear. In this study, the mechanism for the electron transfer at biological/inorganic interface is investigated by integrating molecular modeling with electrochemical and spectroscopic measurements.

Structural Basis for the Effects of Phenylalanine on Tuning the Reduction Potential of Type 1 Copper in Azurin.

In order to investigate the effects of the secondary coordination sphere in fine-tuning redox potentials (°') of type 1 blue copper (T1Cu) in cupredoxins, we have introduced M13F, M44F, and G116F mutations both individually and in combination in the secondary coordination sphere of the T1Cu center of azurin (Az) from . These variants were found to differentially influence the °' of T1Cu, with M13F Az decreasing °', M44F Az increasing °', and G116F Az showing a negligible effect. In addition, combining the M13F and M44F mutations increases °' by 26 mV relative to WT-Az, which is very close to the combined effect of °' by each mutation.

Enhancing sulfate reduction and hydrogen sulfide removal through gas stripping in the acidogenesis phase of a two-phase anaerobic process.

This study aims at evaluating two-phase and single-phase reactors for treating sulfate wastewater with low COD/SO ratios. Additionally, a new process of gas stripping in an acidogenesis phase is proposed to reduce hydrogen sulfide (HS) inhibition and enhance biomethanation. The two-phase performed better than the single-phase in terms of COD removal, CH production and HS resistance.

The impact of powdered activated carbon types on membrane anti-fouling mechanism in membrane bioreactors.

Dosing powdered activated carbon (PAC) has been proven to be an economical and effective method to mitigate membrane fouling. However, the effects of pretreated PAC with different redox properties on membrane fouling still need to be further investigated. Here, the impact of commercial PAC, oxidized-PAC, and reduced-PAC on membrane fouling was investigated in membrane bioreactors (MBRs).

Unexpected role of electron-transfer hub in direct degradation of pollutants by exoelectrogenic bacteria.

Exoelectrogenic bacteria (EEB) are capable of anaerobic respiration with diverse extracellular electron acceptors including insoluble minerals, electrodes and flavins, but the detailed electron transfer pathways and reaction mechanisms remain elusive. Here, we discover that CymA, which is usually considered to solely serve as an inner-membrane electron transfer hub in Shewanella oneidensis MR-1 (a model EEB), might also function as a reductase for direct reducing diverse nitroaromatic compounds (e.g.

Iron Cycle Tuned by Outer-Membrane Cytochromes of Dissimilatory Metal-Reducing Bacteria: Interfacial Dynamics and Mechanisms In Vitro.

The biogeochemical cycle of iron is of great importance to living organisms on Earth, and dissimilatory metal-reducing bacteria (DMRB) with the capability of reducing hematite (α-FeO) by outer-membrane (OM) cytochromes play a great role in the iron cycle. However, the dynamic binding of cytochromes to α-FeO at the molecular level and the resulting impact on the photon-to-electron conversion of α-FeO for the iron cycle are not fully understood. To address these issues, two-dimensional IR correlation analysis coupled with molecular dynamics (MD) simulations was conducted for an OmcA-FeO system as OmcA bonds stronger with hematite in a typical DMRB,.

Roles of cation efflux pump in biomineralization of cadmium into quantum dots in Escherichia coli.

Cadmium (Cd) is a typical and widely present toxic heavy metals in environments. Biomineralization of Cd ions could alleviate the toxicity and produce valuable products in certain waste streams containing selenite. However, the impact of the intrinsic Cd(II) efflux system on the biotransformation process remains unrevealed.

Structural Basis for a Quadratic Relationship between Electronic Absorption and Electronic Paramagnetic Resonance Parameters of Type 1 Copper Proteins.

Type 1 copper (T1Cu) proteins play important roles in electron transfer in biology, largely due to the unique structure of the T1Cu center, which is reflected by its spectroscopic properties. Previous reports have suggested a correlation between a high ratio of electronic absorbance at ∼450 nm to that at ∼600 nm ( = /) and a large copper(II) hyperfine coupling in the direction () in electron paramagnetic resonance (EPR). However, this correlation does not have a clear physical meaning, nor does it hold for many proteins with a perturbed T1Cu center.

Framework of Cytochrome/Vitamin B Linker/Graphene for Robust Microbial Electricity Generation.

A bioelectrochemical system (BES) allows direct electricity production from wastes, but its low-power density, which is mainly associated with its poor anodic performance, limits its practical applications. Here, the anodic performance of a BES can be significantly improved by electrodepositing vitamin B (VB) onto a graphene [reduced graphene oxide (rGO)]-modified glassy carbon electrode (VB/rGO/GC) with Geobacter sulfurreducens as the model microorganisms. The VB/rGO/GC electrode results in 200% higher electrochemical activity than a bare GC anode.

Probing electron transfer between hemin and riboflavin using a combination of analytical approaches and theoretical calculations.

Extracellular electron transfer (EET) occurs from outer-membrane proteins to electron acceptors. Heme(ii) is the active center of outer-membrane proteins and delivers electrons to acceptors or mediators such as riboflavin, a redox active chromophore present in organisms. However, the EET mechanism via mediators, especially the electron transfer process from outer-membrane proteins to mediators, has not been well documented yet.

Roles of 3,3',4',5-tetrachlorosalicylanilide in regulating extracellular electron transfer of Shewanella oneidensis MR-1.

Microbial extracellular electron transfer (EET) is critically involved in many pollutant conversion processes in both natural environment and engineered bioelectrochemical systems (BES), but typically with limited efficiency and poor controllability. In this study, we discover an important role of uncouplers in affecting the microbial energy metabolism and EET. Dose of lower-concentration 3,3',4',5-tetrachlorosalicylanilide (TCS) in the anolyte promoted the current generation and substrate degradation of an MFC inoculated with Shewanella oneidensis MR-1.